Project Info

Neurophylogeny: architecture and development of the nervous system, individually identifiable neurons and the phylogenetic position of the Chaetognatha

The Chaetognatha (arrow worms) are a group of marine carnivores the phylogenetic affinities of which are discussed extremely controversially. Molecular studies have as yet failed to come up with a stable hypothesis on their phylogenetic position. In a wide range of metazoans, the nervous system has proven to provide a wealth of characters for analysing phylogenetic relationships. The goal of the present project is to explore the general layout and development of the central nervous system and individually identifiable neurons by immunohistochemical markers in adult specimens, larvae and embryos of two representatives of the Chaetognatha (Sagitta setosa, Spadella cephaloptera) to elucidate the phylogenetic affinities of this taxon. In order to achieve a maximum comparability with the other neurobiological projects of "Metazoan Deep Phylogeny", we will use the general set of immunohistochemical markers applied in all comparable projects. In addition to these markers, neurogenesis will be monitored in embryos and larvae with two proliferation markers. All taxa that are discussed as being potential sister taxa of the Chaetognatha are being analysed with the similar set of markers in the other projects of "Metazoan Deep Phylogeny" or information about their nervous system is available in the literature. The new information on structure and development of the chaetognath nervous system is expected to contribute new arguments to the discussion on the phylogenetic position of this taxon but also on the organisation of the last common bilaterian ancestor.